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Frequency Response and Harmonic Distortion Testing of Inductive Available online at www.sciencedirect.com Available online at www.sciencedirect.com AvailableScienceDirect online at www.sciencedirect.com Procedia Engineering 00 (2017) 000–000 Procedia Engineering 00 (2017) 000–000 www.elsevier.com/locate/procedia ScienceDirect www.elsevier.com/locate/procedia Procedia Engineering 202 (2017) 159–167 4th International Colloquium "Transformer Research and Asset Management” 4th International Colloquium "Transformer Research and Asset Management” Frequency response and harmonic distortion testing of inductive voltage transformer used for power quality measurements Dalibor Filipović-Grčića, Božidar Filipović-Grčićb*, Danijel Krajtnerc Dalibor Filipović-Grčića, Božidar Filipović-Grčićb*, Danijel Krajtnerc aKončar – Electrical Engineering Institute, Fallerovo šetalište 22, 10000 Zagreb, Croatia a b*UniversityKon ofčar Zagreb, – Electrical Faculty Engineering of Electrical Institute, Engineering Fallerovo and Computing,šetalište 22, Unska10000 3,Zagreb, 10000 Croatia Zagreb, Croatia b *UniversitycKon of čZagreb,ar – Instrument Faculty Transformersof Electrical Engi Inc.,neering Josipa andMokrovi Computing,ća 10, 10000 Unska Zagreb, 3, 10000 Croatia Zagreb, Croatia cKončar – Instrument Transformers Inc., Josipa Mokrovića 10, 10000 Zagreb, Croatia Abstract Abstract International standards related to power quality measurements define methods and accuracies for the measuring instruments, but do not specify Internationalthe accuracy standardsof instrument related transformers. to power qu Therefore,ality measurements it is not possible define meto thodsspecify and an accuracies overall accuracy for the formeasuring such measurements. instruments, butInductive do not voltagespecify transformersthe accuracy of(IVTs) instrument which transformers.are used for Therefore,power quality it is measuremennot possiblets to should specify be an tested overall to accuracydetermine for the such ratio measurements. correction factors Inductive (RCFs) voltage and phasetransformers angle errors (IVTs) at whichhigher frequencies.are used for Inpower this paper,quality harmonic measuremen distortionts should and frebe quencytested toresponse determine tests the are ratio performed correction to dete factorsrmine (RtheCFs) level and of phaseharmonics angle generated errors at higherby IVT frequencies. and its ability In this to paper, transform harmonic harmonics distortion from and high fre quencyvoltage response (HV) to testslow arevoltage performed (LV) toside. dete Complexrmine the volt levelages of consistingharmonics ofgenerated fundamental by IVT voltage and andits abilitycertain toamount transform of superimposed harmonics from harm highonic voltageare used (HV) to check to low the frequencyvoltage (LV) response side. Complexof IVT. RCFs voltages and phaseconsisting angle of errorsfundamental of the IVTvoltage are and determined certain amount and can of be superimposed applied to power harmonic quality are usedmonitors to check for compensationthe frequency ofresponse errors thatof IVT. occur RCFs at high and harmonicphase angle frequencies. errors of theDifferent IVT are test determined circuits are andproposed can be for applied generation to power of HV quality consisting monitors of fundamental for compensation voltage ofand errors harmonic that occurvoltages at highwith amplitudesharmonic frequencies. Different test circuits are proposed for generation inof HV consisting of fundamental voltage and harmonic voltagesrange with 5-15amplitudes % of the applied fundamental voltage. In order to improve thein testing capabilities at higher voltage levels (for equipment rangewith 5-15 % of the applied fundamental voltage. In order to improve the testing capabilities at higher voltage levels (for equipment with 123 kV≤Um≤420 kV), a compensation for both fundamental and harmonic voltages is proposed with a special connection through blocking and pass123 kVfilters.≤Um ≤ 420 kV), a compensation for both fundamental and harmonic voltages is proposed with a special connection through blocking and ©pass 2017 filters. The Authors. Published by Elsevier Ltd. ©Peer-review 2017 The The Authors.under Authors. responsibility Published Published by of Elsevierbythe Elsevierorganizing Ltd. Ltd. committee of ICTRAM 2017. Peer-review under under responsibility responsibility of th ofe organizingthe organizing committee committee of ICTRAM of ICTRAM 2017. 2017. Keywords: Inductive voltage transformer; frequency response; harmonic distortion; power quality; high voltage testing. Keywords: Inductive voltage transformer; frequency response; harmonic distortion; power quality; high voltage testing. 1. Introduction 1. Introduction Voltage harmonic distortion level is one of the significant parameters of power quality in the power system. Higher harmonics causeVoltage the following harmonic effects distortion in electrical level is onenetworks: of the significantadditional parameheatingters and of losses power on quality power insystem the power elements system. (such Higher as transmissio harmonicsn lines,cause thetransformers, following effectscompensation in electrical devices, networks: etc.), additionalunwanted hvoltageeating anddistortion, losses onincreased power system flow ofelements circulating (such currents as transmissio throughn groundinglines, transformers, wire, decrease compensation of transformer devices, rated etc.), power unwanted and inte voltagerference distortion, with conventional increased flowtelecommunication of circulating currentslines. Numerous through problemsgrounding related wire, decreaseto voltage of and transformer current harmonic rated power effects and in intepowerrference systems with are conventional commonly observedtelecommunication nowadays duelines. to Numerousgrowth of largeproblems industrial related consumers to voltage with and currentnon-linear harmonic loads and effects power in powerelectronic systems equipment are commonly [1]. Voltage observed harmonics nowadays may duedisturb to growth sensitive of loadslarge industrialconnected consumers to the grid withand thereforenon-linear they loads should and powerbe limited. electronic Levels equipment and spectral [1]. content Voltage of harmonics voltage distortions may disturb injected sensitive into electricloads connected grids are to tending the grid to andincrease therefore even they though should the beacceptable limited. levelsLevels are and determin spectraled content by numerous of voltage regulations. distortions IEC injected standards into electric grids are tending to increase even though the acceptable levels are determined by numerous regulations. IEC standards * Corresponding author. Tel.: +38516129714; fax: +38516129890. * CorrespondingE-mail address: author. [email protected] Tel.: +38516129714; fax: +38516129890. E-mail address: [email protected] 1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review1877-7058 © under 2017 responsibilityThe Authors. ofPublished the organizing by Elsevier committee Ltd. of ICTRAM 2017. Peer-review under responsibility of the organizing committee of ICTRAM 2017. 1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of ICTRAM 2017. 10.1016/j.proeng.2017.09.703 10.1016/j.proeng.2017.09.703 1877-7058 160 Božidar Filipović-Grčić et al. / Procedia Engineering 202 (2017) 159–167 2 Dalibor Filipović-Grčić et al. / Procedia Engineering 00 (2017) 000–000 [2]-[4] define compatibility levels or planning levels for voltage harmonics in LV, MV and HV networks. Furthermore, European standard [5] defines, describes and specifies the main characteristics of the voltage at a network user's supply terminals in public LV, MV and HV networks under normal operating conditions. According to [6], power quality and voltage distortion measurements are carried out by high accuracy measuring equipment of class A. In MV and HV grids this measuring equipment is commonly connected to secondary side of IVTs installed within the substations. So, an overall accuracy of the measurement depends on the accuracy of IVTs. The accuracy requirements in [6] are defined only for the measuring equipment but not for IVTs. The standard for IVTs [7] defines the accuracy limits at rated frequency, but it doesn’t define the accuracy limits at higher frequencies. The accuracy of IVTs for frequencies higher than the nominal frequency is usually not known. It is therefore difficult to specify an overall accuracy not only for harmonic voltage measurements but also for measurement of any kind of transient containing a wide harmonic spectrum. Literature survey [8]-[17] showed that conventional IVTs may have significant difference between the accuracy at rated frequency and the accuracies at higher frequencies. Therefore, a frequency response of IVTs in the concerned range of frequency should be known to use them for harmonic measurements in power system. Different measuring setups and calculation procedures for frequency response of IVTs are presented in [18]-[21]. Significant differences between IVT ratio at rated frequency and at higher frequencies can be observed, caused by resonances within the IVT. Also, a little research has been conducted concerning the phase angle characteristics of IVTs operating with non-sinusoidal waveforms. To determine the behaviour of the IVT’s ratio and phase angle at higher frequencies two separate tests should be performed: frequency response test and harmonic distortion test. Although different circuit
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